This invention relates to a device, or, in abbreviated form, DME, and a process that makes it possible to collect, distribute, mix, add and/or draw off several fluids (at least one main fluid and at least two secondary fluids).
The invention can be applied in particular in the area of chromatography for fluids in a gaseous state, liquid state or supercritical state.
The invention relates to a DME that can be used in a separation process in a simulated moving bed of paraxylene that is contained in a mixture of xylenes and ethylbenzene, for the purpose of terephthalic acid synthesis, an intermediate petrochemical product in the production of textiles.
The invention can also be used for separating, for example, a xylene and ethylbenzene isomer mixture, a mixture of a compound that is selected from saturated fatty acids and their esters, a mixture of paraffin and olefins, a mixture of isoparaffins and normal paraffins, and other compounds.
The device according to the invention can operate in a liquid phase, a vapor phase or in a supercritical phase and in all of the separation areas, in particular in chemistry, petrochemistry or petroleum.
In the area of separation processes, it is customary to rely on simulated moving bed systems to separate the elements that comprise, for example, at least two different chemical compounds or else two isomers of the same compound. The adsorption material that is used is, for example, a solid.
The technological background that illustrates the implementation of an adsorption device with simulated countercurrent is described in, for example, Pat. U.S.-2,985,589.
In these processes, a main fluid that is introduced via a pump flows through the solid bed along the central axis of the column. To obtain the best performances of this process, it is important that the main fluid flows through the adsorbent according to a piston-type flow (plug flow), i.e., to have a composition and a flow front that are as uniform as possible at all points of the surface of the adsorbent bed.
The prior art describes various means that attempt to obtain and to maintain such a flow.
For applications with simulated countercurrent, the device that is described in U.S. Pat. No. 3,214,247 shows a structure that comprises an upper grid, a lower grid for holding particles and two non-perforated horizontal baffles that are positioned between these two grids. The fluids are added or extracted from a central space between the baffles or deflectors by a hose that traverses the entire section of the device. Such a device makes it possible to remix the main fluid while flowing in the column and also to ensure a good mixing of a fluid that is added to the main fluid.
It is also possible to mention the two U.S. Pat No. 5,792,346 and U.S. Pat. No. 5,755,960 that disclose fluid distribution panels or DME whose function in particular is to mix, extract or add fluids. These DME are connected to fluid distributing-collecting circuits whose function in particular is to homogenize the passage time of the particles of the fluid from outside of the column to the panels and conversely from a panel to an outside collecting network, for example.
Actually, the dispersion into the composition of the flow and in the passage time of the fluid particles can also be obtained in the way in which the fluids are distributed or extracted up to the DME or from the DME.
Some distributing or collecting circuits are suitable for reducing the dispersion time of the fluids. The geometry of these circuits is generally adapted to the geometry of the plates and to the arrangement of the DME at these plates.
For example, in the U.S. Pat. No. 5,792,346, the circuit for distributing or extracting secondary fluids shows a distribution symmetry and an isolength of the transfer lines of the fluids. These circuits allow a distribution of the separator-type fluids or a radial distribution from or to the center of the separation column.
In U.S. Pat. No. 5,755,960, the distributing-collecting circuit consists of several radial hoses that comprise several branches for distributing or collecting secondary fluids to or from each panel that forms a distribution plate. The branches are distributed over the whole or over a portion of the length of the radial-feed hose to which they are connected. Another variant consists in distributing the fluids from a ring or half-rings that are positioned on the periphery of the column. The fluid transfer hoses up to a DME are distributed over the entire length of the ring or half-rings.
The object of this invention is to provide a device that is referred to by the term DME whose function in particular is to collect, mix, extract or remix fluids, that has a specific arrangement of two mixing chambers and a distributing-collecting rail to ensure the most symmetrical distribution or collection of fluids possible.
Its object in particular is to improve the mixing of fluids and thereby the resulting composition. It makes it possible to obtain a plug flow and a flow composition through the adsorbent that is the most homogeneous possible.
Throughout the rest of the description, a level 1 chamber is defined as a chamber whose function is to divide a fluid at least in two or to collect two fluid flows, and a level 2 chamber is defined as a chamber that ensures the division at least in two of a fluid that is obtained from a level 1 chamber or the collection of two fluid flows to send them to a level 1 chamber.
The term DME refers to a panel whose function in particular is to collect, mix, extract or remix one or more fluids.
This invention relates to a device (DME in abbreviated form) or panel for collecting, distributing, mixing or drawing off several fluids, at least one main fluid and at least two secondary fluids, that comprises at least:
means for collecting a main fluid,
at least two injection and/or draw-off rails that allow the passage of secondary fluids,
at least two mixing chambers that communicate with injection and/or draw-off rails with orifices or passages,
means for redistributing the fluid that is obtained from said mixing chambers,
means (5a, 5b) for separating collecting and redistributing means.
It is characterized in that the rails are arranged one above the other and in that said mixing chambers are arranged on both sides of at least one of said rails.
The mixing chambers are arranged, for example, relative to the orifices to obtain an injection or a draw-off of the fluid or fluids that is the most uniform possible in the mixing chamber or chambers.
The injection rails and the mixing chambers are located, for example, approximately in the center of gravity of the surface of said DME.
The upper rail can be provided with at least two hoses, and the lower rail can be provided with at least one hose, whereby the hoses are arranged to ensure the circulation of secondary fluids most symmetrically in the rails and the mixing chambers.
The passage openings of a secondary fluid of the rail or rails whose function is to inject secondary fluids into a mixing chamber have an axis such that the fluid that is obtained strikes at least a portion of a solid wall of one of the elements of the DME.
The lower circuit or lower rail of the secondary fluid has its lower wall arranged, for example, at the lower grid (to improve the mechanical behavior of the unit).
This invention also relates to a device or a column for separation that comprises, for example, a chamber, whereby the chamber comprises at least a first adsorbent bed (A1) and at least a second adsorbent bed (A2), whereby the beds are separated by a plate Pi that comprises one or more panels (DME) that have one of the characteristics of Claims 1 to 5, whereby the DME are connected with the outside via connecting hoses.
The upper rail of a DME may have a function of collecting fluids, and the lower rail of a DME may have a function of injecting fluids.
The upper rail of a DME has, for example, a function of injecting fluids, and the lower rail of a DME has a function of collecting fluids.
The upper and lower rails of a DME may each have a fluid injecting-collecting function.
The openings of the rail or rails that have an injection function are arranged, for example, such that the fluid jet that passes through the orifice strikes at least one portion of a solid wall of one of the elements of the DME.
The openings of the rails can be arranged alternately or at random.
The parameters of the rails and the openings are selected, for example, from among the following data:
a diameter of the openings of, for example, between 2 and 15 mm and preferably between 4 and 7 mm, whereby the openings may have an injection function,
a perforation span of between 25 and 400 mm and preferably between 50 and 200 mm,
a rate of flow of the fluids of between 3-20 m/s and preferably between 5-15 m/s; the value of the span that is under consideration with the value of the rate makes it possible to obtain a good mixing of the secondary fluid and the main fluid.
The parameters of the mixing chambers and the openings of the chambers are selected, for example, from among the following values:
a diameter of openings of between 5 and 50 mm, and preferably between 10 and 25 mm,
a perforation span that is selected from the interval 25-400 mm and preferably in the interval of 50-200 mm,
a rate of flow of the mixture of between 0.5 and 3.5 m/s and preferably between 1.0-2.0 m/s.
The device may comprise at least two fluid distribution systems that have the following characteristics:
said distribution system is placed on the periphery of said chamber,
said distribution system is connected with at least one distribution plate (Pi), and said distribution system comprises:
at least one hose that makes it possible for the device and the outside to communicate,
at least one so-called level 1 chamber (N1) that ensures a two-way division or collection of the fluid flow, whereby said chamber is connected with the communication hose,
at least two so-called level 2 chambers (N20, N21), whereby the level 2 chambers ensure a two-way division or collection of the flow of the fluid that comes from or is sent to level 1 chamber (N1),
one or more connecting hoses (C(N20)j, C(N21)j)) that extend between a level 2 chamber (N20, N21) and at least one of panels (DME) of a plate (Pi), whereby points rj for connecting connecting hoses are located in a zone (Z20, Z21), whereby the positioning of this zone is determined by an angle xcex1 counting from one of the radial axes of said plate (Pi), whereby each of the fluid connecting hoses has a length li, whereby the value of each of lengths li, of angle xcex1 and of length Zr of the zone are selected so that the passage time of the fluids between a panel (DME) of a plate (Pi) and the hose for introducing or extracting the fluids is essentially identical for all of the fluids.
The minimum dispersion time that is obtained is equal to, for example, the difference in time between the first and the last hole of supplied DME, which is at most 10 s and preferably less than, 5 s.
Plate Pi can be divided into four sectors.
Each plate is divided into, for example, several panels or DME according to a cutaway in parallels (of meridian type).
Angle xcex1 is, for example, between 30 and 90 degrees, preferably between 50 and 60 degrees, and length Zr that corresponds to the angle sector is between 3 and 30 degrees and preferably between 7 and 15 degrees.
This invention also relates to a process that makes it possible to separate at least one compound from a mixture or an element by adsorption. It is characterized in that a main fluid, from which it is sought to separate some compounds, is brought into contact with an adsorbent that is selected as a function of its ability to separate the compounds, and the secondary fluids are injected and/or extracted via a panel or DME to collect, distribute, mix or draw-off several fluids, at least one main fluid and at least two secondary fluids, that comprises at least:
means for collecting a main fluid,
at least two injection and/or draw-off rails that allow the passage of secondary fluids,
at least two mixing chambers that communicate with injection or draw-off rails with orifices or passages,
means for redistributing the fluid that is obtained from said mixing chambers,
means for separating collecting and redistributing spaces, whereby the rails are arranged one above the other, and the mixing chambers are arranged on both sides of the rails.
It is possible to inject a fluid in the most uniform manner possible into the mixing chambers by passing through the orifices whose function is injection.
It is possible to group the fluids by function (injection/or draw-off) or by nature or by flow rate value.
The device and the process according to the invention are well suited for separating a feedstock by chromatography for fluids in a gaseous state, liquid state or supercritical state.
The device and the process according to the invention are also well suited for the separation of paraxylene in a simulated moving bed.
Relative to the devices of the prior art, the DME according to the invention and the separation device that comprises one or more of these DME have in particular the following advantages:
because of the good distribution symmetry of the secondary fluids and the main fluid, the mixing is improved over the entire plate, which imparts a more homogenous composition and a general plug flow to the circulating flow in the separation device,
the distribution or the extraction of fluids in or from a DME is carried out with a distributing-collecting system that ensures a minimum dispersion between the passage times of the fluid flows for the same plate,
an approximately uniform flow density over the entire column,
a homogeneous spatial distribution of the flows of secondary fluids over the surface of the plate.